Abstract: A cutting tool is operatively connected with the piston of a tool positioning cylinder so as to move in response to axial movement of the piston. One end of the cylinder is connected with one end of a stroke limiting cylinder to form a closed fluid circuit therebetween. The piston of the stroke limiting cylinder has a predetermined adjustable stroke. A metering system is provided for injecting or extracting incremental fixed volumes of oil to and from the closed fluid circuit to increase or decrease the stroke of the piston in the tool positioning cylinder and thereby vary the depth of cut of the tool.